There is a growing interest in the development of processes for polymerizing olefins such as ethylene and propylene in the vapor phase and in the absence of any liquid solvents. In carrying out such polymerizations, preformed particles of the desired olefin polymer are fluidized in a reactor by either gas flow or machanical means. Finely divided catalyst particles are introduced into the reactor to initiate polymerization of the vaporized monomer on the fluidized olefin polymer particles. In carrying out such processes, it is desirable to employ highly active catalysts to minimize the catalyst residues left in the polymers produced by such processes. Frequently the active catalysts employed are supported on fine particles of olefin polymer. A typical example of the type of catalysts employed is the magnesium chloride-modified, titanium containing catalyst of the type disclosed in U.S. Pat. No. 4,021,599.
In carrying out such polymerizations employing such solid catalysts, the catalyst feed line introducing the catalyst particles to the reactor must have very small internal diameters. Difficulties are sometimes encountered in feeding such catalysts to the polymerization reactor where oversized catalyst particles are introduced into the catalyst feed lines. It becomes a matter of considerable importance to have available catalyst particles of a highly homogeneous nature, all of which are smaller than a prescribed maximum diameter.